Ancient philosophers believed that the Earth and humankind were crucial for the workings of the universe. To them the solar system was essentially the universe. The earliest models of the solar system followed the teachings of Aristotle and were geocentric in nature. It was accepted that the Earth was at the centre of the universe, and that everything else moved around it.
Nevertheless, some ancient Greek astronomers did not accept this notion. One such astronomer was named Aristarchus. He thought that the Earth and all the other planets orbited the Sun. This was not widely accepted, because most people did not want to believe that the Earth was not the centre of everything.
Later a Polish clerk, Nicholas Copernicus, rediscovered the heliocentric model and showed why it better fit the observed motion of the planets. Eventually it became accepted, but it was not easy to convince people. It was difficult to place the Earth in such a non-central place in the universe.
However, it was still believed that the Earth was important enough to orbit a star which was at the centre of the universe. It was not known until later that we live on a rather ordinary planet which orbits an ordinary star which is one of a huge collection of stars called the Milky Way Galaxy. Not only that, but the Sun is not even the centre of the galaxy, it is merely near the edge. The Milky Way is not unique either. There are billions of galaxies spread throughout the observable universe, and the Milky Way is one of them - it is not at the centre of the Universe.
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This article appeared in the April 1996 newsletter.